Recently LANs have taken on added significance in the field of computer systems. Current advancements point to the desirability of interconnecting computers on an organization-wide basis to obtain more overall distributed computing capacity. LANs are the means by which computers are typically interconnected on an effective basis for this purpose.
As the computing capacities of computers have continued to increase, the data transfer capacities of LANs have remained more or less the same for the past few years. This is because each LAN has its own predetermined operational protocol, and that protocol tends to be the limiting factor on the maximum amount of data which can be transferred. Since adhering to this operational protocol is critical to the proper operation of a LAN, and because the protocol tends to be fixed as an unalterable part of the design implementation of a LAN, improvements in LAN capacity have centered more around efficiency in the software which delivers data to and receives data from the LAN, but not in the operating capacity of the LAN itself. Such software improvements have generally not resulted in substantially enhanced LAN capacities.
LANs of different operational capacities are available. However, LANs of high capacities have tended to require special equipment, are significantly expensive, and have usually been implemented for special purposes rather than common use. The less expensive, more commonplace LANs have tended to have only moderate or low data transfer capacities. While the more commonplace LANs are satisfactory for some purposes, they can easily become a significant overall limitation in networking computers together to achieve system-wide, increased computing capacity.
In many network situations the use of a high capacity, more expensive, special purpose LAN cannot be justified from an overall standpoint. While high capacity devices such as graphics work stations, computational accelerators and file servers can utilize the higher LAN capacity, the number of high capacity devices on the network may be small compared to the number of relatively low capacity devices. The low capacity devices will generally have no need to utilize the higher capacity of a special purpose LAN. Significant expense will be encountered to establish a high capacity network for all of the devices, particularly when a pre-existing network must be replaced. However, failure to do so can result in a significant limitation in overall system-wide capacity because the operational throughput of the relatively small number of high capacity devices is limited by the capacity of the LAN.